DNS Forwarding and Conditional Forwarding

This video will look at how DNS forwarding works and how conditional forwarding works. Forwarding is when a DNS request is forwarded from one DNS server to another. Conditional forwarding is when a condition is applied to which DNS requests are forwarding and which are not.Download the PDF handoutDNS ForwardingDNS forwarding is the process of forwarding a DNS request from one DNS server to another. The most common example of this is when a company forwards its internal DNS server to its ISP’s DNS server. Since the ISP DNS server will receive a lot more resolve requests than the internal DNS server, there is a higher possibility that when a client asks for a DNS hostname to be resolved, the DNS server may have resolved the DNS name previously and have it stored in the DNS cache, meaning the hostname will not need to be resolved again.DNS ForwardingIn some companies, they may want to prevent their internal DNS servers accessed by not having them directly accessible on the internet. To do this, a DMZ is created with a DNS server that has access to the internet. The company then uses another DNS server on their internal network. This internal DNS server forwards requests to the DMZ DNS server which forwards DNS requests to the ISP’s DNS server. This means the internal DNS server does not access the internet directly and thus helps protect it. If the DMZ DNS server was to be attacked, the DNS records on the internal DNS would be protected.Conditional ForwardingConditional forwarding is only performed if a condition is met. In this example, DNS requests for the other domain are forwarded to the other company’s DNS server. All other DNS requests are forwarded directly to the ISP’s DNS server.